The influence of cypermethrin and oxydemeton‐methyl treatment on Lygus damage in young Scots pine seedlings

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Abstract
Summary: Laboratory experiments were carried out to evaluate the efficiency of two insecticides, cypermethrin and oxydemeton‐methyl, in controlling the nymphs and adults of Lygus bugs and the resulting damage caused by these bugs to small pine seedlings. Both insecticides significantly increased the mortality of bugs on the seedlings compared with bug mortality on untreated controls. Mortality of bugs was higher in the oxydemeton‐methyl treatment than in the cypermethrin treatment. The occurrence of seedlings with multiple leaders and the number of leader shoots per seedling were significantly decreased in insecticide‐treated seedlings. Mean number of leader shoots was significantly higher in seedlings treated with oxydemeton‐methyl than in seedlings treated with cypermethrin after a 24‐h exposure to nymphal instars of Lygus. The mortality of the pine seedlings was very low but significantly decreased in insecticidal treatments. Factors affecting the effects of different insecticides on bug mortality and their efficiency in controlling the multiple‐leadering phenomenon are discussed.